1. 1. Melt the butter in a large, heavy saucepan over moderate heat, add the ham and scallions, and cook, stirring now and then, for 5 to 8 minutes or until lightly browned.
2. 2. Add the beans and broth and bring to a boil. Adjust the heat so the broth bubbles gently, cover, and cook for 12 to 15 minutes or until the beans are crisp-tender.
3. 3. Meanwhile, combine the thickener and the mustard and set aside. As soon as the beans are done, whisk a little of the hot broth into the mustard mixture, stir back into the pan, add the pepper, and cook, stirring constantly, for 3 minutes or until the broth thickens. Continue cooking uncovered, stirring occasionally, for 3 to 5 minutes or until the sauce has the consistency of a glaze.
4. 4. Taste the beans for salt and pepper, adjust as needed, and serve straightaway.
5. From the book A Love Affair with Southern Cooking: Recipes and Recollections by Jean Anderson. Copyright © 2007 Jean Anderson. Reprinted by permission of William Morrow Cookbooks, an imprint of HarperCollins Publishers.